1. Field of the Invention
The present invention relates to a vehicle detection apparatus and a vehicle detection method which can detect a desired vehicle by using a microphone array.
2. Description of the Related Art
There have so far been proposed a wide variety of apparatuses for detecting the state of traffic flow from the noises produced by vehicles, and such proposed apparatuses include those intended for reducing the sizes and costs of the apparatuses. An exemplified apparatus is shown in FIG. 16, as comprising sound collectors 701 and 702, amplifying circuits 703 and 704, a switching circuit 705, a frequency analyzing circuit 706, a frequency distribution comparing circuit 707, a time difference detecting circuit 708, a time difference/velocity converting circuit 709, a timing controlling circuit 710 and a velocity display outputting circuit 711 and determines the velocity of traffic flow by measuring noises at the two spots along and in the vicinity of a road where traffic flows (Japanese Patent Application Laid-Open No. 114098/1993).
In FIG. 16, the first sound collector 701 and the second sound collector 702 are placed along traffic flow with a fixed distance L therebetween. The noises A and B of the traffic flow which have been collected by these sound collectors 701 and 702 are in turn inputted to the frequency analyzing circuit 706 by switching the switching circuit 705 alternately, and their frequencies are in turn analyzed by the frequency analyzing circuit 706, to ensure that frequency spectral distributions SA and SB are obtained.
Then, the degree of similarity between the frequency spectral distribution SA and the frequency spectral distribution SB is detected by the frequency distribution comparing circuit 707, and the time difference between the frequency spectral distribution SA and the frequency spectral distribution SB which nearly match with each other is determined by the time difference detecting circuit 708. The time difference/velocity converting circuit 709 determines the velocity V of a noise source (vehicle) by performing the computation represented by the expression xe2x80x9cV=L/dtxe2x80x9d. In this case, the direction in which the vehicle in headed can be calculated from the calculated time difference.
However, such a conventional detection apparatus has the problem that the accuracy of detecting a vehicle lowers when a plurality of vehicles are traveling simultaneously or when there are noises produced from something other than a desired vehicle because, as described above, the conventional detection apparatus measures noises only at the two spots along and in the vicinity of a road where traffic flows and calculates the velocity and traveling direction of the vehicle based on the time difference between the frequency spectral distribution SA and the frequency spectral distribution SB which nearly match with each other.
It is an object of the present invention to provide a vehicle detection apparatus which is capable of detecting a sound source even when a plurality of vehicles are traveling simultaneously or when there are noises produced from something other than the desired vehicle and calculating the location in the vehicle traveling direction and the lane direction of the vehicle and the number of passing vehicles.
It is another object of the present invention to provide a vehicle detection method which is capable of detecting a sound source even when a plurality of vehicles are traveling simultaneously or when there are noises produced from something other than the desired vehicle and calculating the location in the vehicle traveling direction and the lane direction of the vehicle and the number of passing vehicles.
In accordance with a first aspect of the present invention, there is provided a vehicle detection apparatus which comprises a sound collection means comprising a plurality of microphones and placed in the vicinity of a road; a direction estimation means for sampling the input signals from the sound collection means periodically with time windows and estimating the direction of a sound source in each time window; and a similarity calculation means for calculating the degree of similarity between the estimation results by the direction estimation means and a plurality of templates which indicate a change in the location of the sound source with time while the vehicle is traveling. According to this constitution, a change in the location of the vehicle with time is detected by calculating the above degree of similarity, whereby the vehicle is detected.
In the aforesaid vehicle detection apparatus according to the present invention, the above sound collection means comprises a plurality of microphones aligned on a line parallel to the vehicle traveling direction. According to this constitution, the location in the vehicle traveling direction of a vehicle is detected.
In the aforesaid vehicle detection apparatus according to the present invention, the above sound collection means comprises a plurality of microphones aligned on a line parallel to the vehicle traveling direction and a plurality of microphones aligned on a line perpendicular to the vehicle traveling direction. According to this constitution, the location in the vehicle traveling direction and the lane direction of a vehicle is detected.
In the aforesaid vehicle detection apparatus according to the present invention, the above sound collection means comprises a plurality of microphones aligned on a line parallel to the vehicle traveling direction and a plurality of microphones aligned on a line perpendicular to the vehicle traveling direction. According to this constitution, the location in the vehicle traveling direction and the lane direction of a vehicle is detected. In this case, the above direction estimation means comprises an estimation means for estimating the location in the vehicle traveling direction and the lane direction of the sound source.
In the aforesaid vehicle detection apparatus according to the present invention, the above sound collection means comprises a plurality of microphones aligned on a line parallel to the vehicle traveling direction and a plurality of microphones aligned on a line perpendicular to the vehicle traveling direction. According to this constitution, the location in the vehicle traveling direction and the lane direction of a vehicle is detected. In this case, when the above road has a plurality of lanes, the vehicle detection apparatus according to the present invention comprises counters for counting the estimation results by the above direction estimation means for each lane and a lane detection means for detecting the location in the lane direction of the sound source based on the counting values of these counters.
In the aforesaid vehicle detection apparatus according to the present invention, the above sound collection means comprises a plurality of microphones arranged in the form of a matrix in the same plane. According to this constitution, even when a plurality of vehicles are traveling simultaneously, the microphones arranged in the form of a matrix identifies a sound source precisely and detects the location in the vehicle traveling direction and the lane direction of the vehicle while the deterioration of the accuracy of the detection by other noises is suppressed.
In the aforesaid vehicle detection apparatus according to the present invention, the above direction estimation means comprises an estimation means for estimating the two-dimensional direction in the vehicle traveling direction and the lane direction of a sound source. According to this constitution, the location in the vehicle traveling direction and the lane direction of the vehicle can be detected while the deterioration of the accuracy of the detection by other noises is suppressed more securely, as compared with, for example, the case where microphones are aligned in the x-axis and z-axis directions to set only an xcex1 direction (lane direction) or a xcex2 direction (vehicle traveling direction).
In the aforesaid vehicle detection apparatus according to the present invention, the above direction estimation means comprises an estimation means for estimating the direction in the vehicle traveling direction and the lane direction of a sound source two-dimensionally. According to this constitution, the location in the vehicle traveling direction and the lane direction of the vehicle can be detected while the deterioration of the accuracy of the detection by other noises is suppressed more securely, as compared with, for example, the case where microphones are aligned in the x-axis and z-axis directions to set only an xcex1 direction (lane direction) or a xcex2 direction (vehicle traveling direction). In this case, the above direction estimation means comprises an estimation means for estimating the direction of a sound source by scanning in the vehicle traveling direction with the direction of the sound source in the lane direction limited to the center of the road.
In the aforesaid vehicle detection apparatus according to the present invention, the above direction estimation means comprises an estimation means for estimating the direction in the vehicle traveling direction and the lane direction of a sound source two-dimensionally. According to this constitution, the location in the vehicle traveling direction and the lane direction of the vehicle can be detected while the deterioration of the accuracy of the detection by other noises is suppressed more securely, as compared with, for example, the case where microphones are aligned in the x-axis and z-axis directions to set only an xcex1 direction (lane direction) or a xcex2 direction (vehicle traveling direction). In this case, the above direction estimation means comprises an estimation means for estimating the direction of a sound source by scanning in the lane direction with the direction of the sound source in the vehicle traveling direction limited.
In the aforesaid vehicle detection apparatus according to the present invention, when the above road has a plurality of lanes, comprises a first counter which counts the estimation results by the above direction estimation means for each lane, a lane location detection means for detecting the location in the lanes of a sound source based on the counting values of this counter, and a second counter which counts the detection results by this lane location detection means for each lane. According to this constitution, passing vehicles are counted for each lane by the above second counter.
In the aforesaid vehicle detection apparatus according to the present invention, the above similarity calculation means comprises a comparison means for comparing the above plurality of templates with the estimation results. According to this constitution, the traveling velocity of a vehicle is calculated by using the templates (plurality of templates) at different velocities.
In the aforesaid vehicle detection apparatus according to the present invention, the above similarity calculation means comprises a comparison means for comparing the above plurality of templates with the estimation results. According to this constitution, the traveling velocity of a vehicle is calculated by using the templates (plurality of templates) at different velocities. In this case, the above plurality of templates are preferably those prepared by using the sounds of a vehicle when the vehicle is caused to travel at different velocities.
In the aforesaid vehicle detection apparatus according to the present invention, the above similarity calculation means comprises a comparison means for comparing the above plurality of templates with the estimation results. According to this constitution, the traveling velocity of a vehicle is calculated by using the templates (plurality of templates) at different velocities. In this case, the above plurality of templates are preferably those prepared by expanding or contracting the time base of a template prepared by using the sound of a vehicle traveling at a constant velocity, and the above similarity calculation means comprises a time-base expansion means for expanding or contracting the above time base of the template.
In the aforesaid vehicle detection apparatus according to the present invention, the above sound collection means comprises a plurality of microphones the number of which is equal to or greater than xe2x80x9cnumber of assumed sound sources+1xe2x80x9d. According to this constitution, the accuracy of estimating the direction of a sound source improves, and the vehicle can still be detected even when a plurality of vehicles are traveling simultaneously or when there are noises produced from something other than the desired vehicle.
In accordance with a second aspect of the present invention, there is provided a vehicle detection method which comprises a sound collection step in which the noises produced by a traveling vehicle are collected by a plurality of microphones placed in the vicinity of a road; a direction estimation step in which the input signals from the above plurality of microphones are sampled periodically with time windows and the direction of a sound source is estimated in each time window; and a similarity calculation step in which the degree of similarity between the estimation results by this direction estimation step and templates which indicate a change in the direction of the sound source with time while the vehicle is traveling is calculated. According to this method, a change in the location of the vehicle with time is detected by calculating the above degree of similarity, whereby the vehicle is detected.
The aforesaid vehicle detection method according to the present invention may comprises a sound collection step in which the noises produced by a traveling vehicle are collected by a plurality of microphones aligned on a line parallel to the vehicle traveling direction and placed in the vicinity of a road; a direction estimation step in which the input signals from the above plurality of microphones are sampled periodically with time windows and the direction of a sound source is estimated in each time window; and a vehicle detection step in which the degree of similarity between the estimation results by this direction estimation step and a plurality of templates which indicate a change in the direction of the sound source with time while the vehicle is traveling is calculated and the vehicle is detected based on the result of the calculation. According to this method, a change in the location in the vehicle traveling direction of the vehicle with time is detected by calculating the above degree of similarity, whereby the vehicle is detected, and the traveling velocity of the vehicle is calculated by using the templates (plurality of templates) at different velocities.
The aforesaid vehicle detection method according to the present invention may comprises a sound collection step in which the noises produced by a traveling vehicle are collected by a plurality of microphones aligned on a line parallel to the vehicle traveling direction and on a line perpendicular to the vehicle traveling direction and placed in the vicinity of a road; a direction estimation step in which the input signals from the above plurality of microphones are sampled periodically with time windows and the direction in the vehicle traveling direction and the lane direction of a sound source is estimated in each time window; a vehicle detection step in which the degree of similarity between the estimation results in the vehicle traveling direction by this direction estimation step and a plurality of templates which indicate a change in the direction of the sound source with time while the vehicle is traveling is calculated and the vehicle is detected based on the result of the calculation; and a lane detection step in which the estimation results in the lane direction by the above direction estimation step are counted for each lane and the location in the lanes of the sound source is detected based on the counting values. According to this method, the location in the traveling direction and the lane direction of the vehicle is detected.
The aforesaid vehicle detection method according to the present invention may comprises a sound collection step in which the noises produced by a traveling vehicle are collected by a plurality of microphones arranged in the form of a matrix in the same plane and placed in the vicinity of a multi-lane road; a direction estimation step in which the input signals from the above plurality of microphones are sampled periodically with time windows and the two-dimensional direction in the vehicle traveling direction and the lane direction of a sound source is estimated in each time window; a vehicle detection step in which the degree of similarity between the estimation results in the vehicle traveling direction by this direction estimation step and a plurality of templates which indicate a change in the direction of the sound source with time while the vehicle is traveling is calculated and the vehicle is detected based on the result of the calculation; and a lane detection step in which the estimation results in the lane direction by the above direction estimation step are counted for each lane and the location in the lanes of the sound source is detected based on the counting values. According to this method, the location in the vehicle traveling direction and the lane direction of the vehicle can be detected while the deterioration of the accuracy of the detection by other noises is suppressed more securely, as compared with, for example, the case where microphones are aligned in the x-axis and z-axis directions to set only an xcex1 direction (lane direction) or a xcex2 direction (vehicle traveling direction).
The aforesaid vehicle detection method according to the present invention may comprises a sound collection step in which the noises produced by a traveling vehicle are collected by a plurality of microphones arranged in the form of a matrix in the same plane and placed in the vicinity of a multi-lane road; a direction estimation step in which the input signals from the above plurality of microphones are sampled periodically with time windows and the two-dimensional direction in the vehicle traveling direction and the lane direction of a sound source is estimated in each time window; a vehicle detection step in which the degree of similarity between the estimation results in the vehicle traveling direction by this direction estimation step and a plurality of templates which indicate a change in the direction of the sound source with time while the vehicle is traveling is calculated and the vehicle is detected based on the result of the calculation; and a lane detection step in which the estimation results in the lane direction by the above direction estimation step are counted for each lane and the location in the lanes of the sound source is detected based on the counting values. According to this method, the location in the vehicle traveling direction and the lane direction of the vehicle can be detected while the deterioration of the accuracy of the detection by other noises is suppressed more securely, as compared with, for example, the case where microphones are aligned in the x-axis and z-axis directions to define only an xcex1 direction (lane direction) or a xcex2 direction (vehicle traveling direction). In this case, in the above direction estimation step, the direction of the sound source is estimated by scanning in the vehicle traveling direction with the direction of the sound source in the lane direction limited to the center of the road.
The aforesaid vehicle detection method according to the present invention may comprises a sound collection step in which the noises produced by a traveling vehicle are collected by a plurality of microphones arranged in the form of a matrix in the same plane and placed in the vicinity of a multi-lane road; a direction estimation step in which the input signals from the above plurality of microphones are sampled periodically with time windows and the two-dimensional direction in the vehicle traveling direction and the lane direction of a sound source is estimated in each time window; a vehicle detection step in which the degree of similarity between the estimation results in the vehicle traveling direction by this direction estimation step and a plurality of templates which indicate a change in the direction of the sound source with time while the vehicle is traveling is calculated and the vehicle is detected based on the result of the calculation; and a lane detection step in which the estimation results in the lane direction by the above direction estimation step are counted for each lane and the location in the lanes of the sound source is detected based on the counting values. According to this method, the location in the vehicle traveling direction and the lane direction of the vehicle can be detected while the deterioration of the accuracy of the detection by other noises is suppressed more securely, as compared with, for example, the case where microphones are aligned in the x-axis and z-axis directions to set only an xcex1 direction (lane direction) or a xcex2 direction (vehicle traveling direction). In this case, in the above direction estimation step, the direction of the sound source is estimated by scanning in the lane direction with the direction of the sound source in the vehicle traveling direction limited.
The aforesaid vehicle detection method according to the present invention may comprises a sound collection step in which the noises produced by a traveling vehicle are collected by a plurality of microphones arranged in the form of a matrix in the same plane and placed in the vicinity of a multi-lane road; a direction estimation step in which the input signals from the above plurality of microphones are sampled periodically with time windows and the two-dimensional direction in the vehicle traveling direction and the lane direction of a sound source is estimated in each time window; and a lane-specific vehicle detection step in which the estimation results in the lane direction by this direction estimation step are counted for each lane to carry out vehicle detection and detected vehicles are counted for each lane. According to this method, passing vehicles are counted for each lane while the deterioration of the accuracy of the detection by other noises is suppressed more securely, as compared with, for example, the case where microphones are aligned in the x-axis and z-axis directions to set only an xcex1 direction (lane direction) or a xcex2 direction (vehicle traveling direction).
The aforesaid vehicle detection method according to the present invention may comprises a sound collection step in which the noises produced by a traveling vehicle are collected by a plurality of microphones arranged in the form of a matrix in the same plane and placed in the vicinity of a multi-lane road; a direction estimation step in which the input signals from the above plurality of microphones are sampled periodically with time windows and the two-dimensional direction in the vehicle traveling direction and the lane direction of a sound source is estimated in each time window; and a lane-specific vehicle detection step in which the estimation results in the lane direction by this direction estimation step are counted for each lane to carry out vehicle detection and detected vehicles are counted for each lane. According to this method, passing vehicles are counted for each lane while the deterioration of the accuracy of the detection by other noises is suppressed more securely, as compared with, for example, the case where microphones are aligned in the x-axis and z-axis directions to set only an xcex1 direction (lane direction) or a xcex2 direction (vehicle traveling direction). In this case, in the above direction estimation step, the direction of the sound source is estimated by scanning in the lane direction with the direction of the sound source in the vehicle traveling direction limited.
In the above vehicle detection step of the aforesaid vehicle detection method according to the present invention, the degree of similarity between the templates prepared by using the sounds of a vehicle traveling at different velocities and the above estimation results in the above vehicle detection step is calculated. According to this method, a change in the location in the vehicle traveling direction of the vehicle with time is detected by calculating the above degree of similarity, whereby the vehicle is detected, and the traveling velocity of the vehicle is calculated by using the templates (plurality of templates) at different velocities.
In the vehicle detection method according to the present invention, the above vehicle detection step further comprises a velocity detection step in which the degree of similarity between the templates prepared by expanding or contracting the time base of a template prepared by using the sounds of a vehicle traveling at a constant speed and the above estimation results is calculated and, according to the result of the calculation, the velocity of the detected vehicle is calculated from the expansion ratio of the template and the vehicle velocity used for preparing the template. According to this method, a change in the location in the vehicle traveling direction of the vehicle with time is detected by calculating the above degree of similarity, whereby the vehicle is detected, and the traveling velocity of the vehicle is calculated by using the templates (plurality of templates) at different velocities.
In the aforesaid vehicle detection method according to the present invention, template matching is used to calculate the degree of similarity between the above templates and the estimation results. According to this method, a change in the location of the vehicle with time is detected by calculating the above degree of similarity, whereby the vehicle is detected. A change in the location of the vehicle with time is detected by calculating the above degree of similarity, whereby the vehicle is detected in the vehicle traveling direction.
In the aforesaid vehicle detection method according to the present invention, DP matching is used to calculate the degree of similarity between the templates and the estimation results. According to this method, a change in the location of the vehicle with time is detected by calculating the above degree of similarity, whereby the vehicle is detected. A change in the location of the vehicle with time is detected by calculating the above degree of similarity, whereby the vehicle is detected in the vehicle traveling direction.
In the aforesaid vehicle detection method according to the present invention, the number of the above plurality of microphones is equal to or greater than xe2x80x9cnumber of assumed sound sources+1xe2x80x9d. According to this method, the accuracy of estimating the direction of a sound source improves, and a vehicle is detected even when a plurality of vehicles are traveling simultaneously or when there are noises produced from something other than the desired vehicle.